When drilling undergrounds well such as for oil, gas or water, a borehole is drilled from the surface to the fluid bearing formation. Such formations often have significant horizontal extent but a limited vertical extent. Therefore it is advantageous to drill non-vertical boreholes, also called deviated, lateral or horizontal boreholes, in the subterranean production zone (the reservoir) to increase the production flow rate of the fluids from the lateral to the main borehole. Often these lateral boreholes are boreholes drilled from a main vertical borehole, see FIG. 10. These lateral holes departing from an existing borehole into the production fluid reservoir are called drain holes.
The lateral drain holes can be unconsolidated and to maintain their stability the boreholes can be kept open by inserting tubular liners down at least a partial and up to a total length of the borehole. Perforated liners are used in sand control applications in lateral boreholes. In this type of application generally wire, wire mesh or filtering screens are wrapped around and welded to the perforated liner, which is a base pipe, to filter out sand from fluid drawn out of the reservoir. For example the sands control screens described in WO 03091535 and U.S. Pat. No. 5,849,188.
One of the problems with lateral wells is that to deploy a liner or other downhole tool into the lateral borehole requires the liner to have the ability to negotiate the bend from a tool deployed down the main borehole into the lateral drain holes, as the lateral drain holes are typically formed at an angle of 90° from the main borehole. A guide that is part of the tool deploying the liner causes the liner to bend, so that it can go from the main borehole to the lateral drain hole, and applies curvature to the liner and orientates the liner into the formation. However the base pipes of the liners often do not provide much flexibility for inserting the liner into a lateral borehole from a main borehole.
This invention provides a liner that is flexible so it can be easily deployed into a lateral drain hole that is at any angle from the main borehole.